10 Royal Poinciana or Flamboyant Heirloom Seeds 10 Royal Poinciana or Flamboyant Tree seeds it usually grows to a modest height (mostly 5 meters, but it can reach an maximum height of 12 meters) but spreads widely The Royal Poinciana is most commonly propagated by seeds. Seeds are collected, soaked in warm water for at least 24 hours, and planted in warm, moist soil in a semi-shaded, sheltered position. The Royal Poinciana requires a tropical or near-tropical climate, but can tolerate drought and salty conditions. The Poinciana prefers an open, free-draining sandy or loamy soil enriched with organic matter.